Core impact force of vertical water jets on smooth and rough surfaces

Document Type : Article

Authors

1 Water Science Engineering Department, Shahid Chamran University, Ahwaz, Iran

2 Department of Water Engineering, Sari Agricultural Science and Natural Resources University, Sari, Iran

3 School of Water Science and Engineering, Shahid Chamran University of Ahvaz, Iran

Abstract

A normal way to dissipate energy of the dam released high velocity jets is to allow them to free-fall in to a plunge pool or impact a plane surface in case of dam site limitations. The water jets have an undisturbed core from nozzle outlet to a certain falling height, which has more impact force and less turbulent intensity than the developed part of the free jet. Experiments are conducted to determine core impact pressure coefficient of a vertical jet on smooth and rough plane surfaces. The experiment results for different jet diameters and falling heights showed considerable increase of the mean dynamic pressure coefficient with increase of the jet Froude number for both smooth surface and rough surface. A simple Froude based mathematical model is correlated for estimation of jet core impact force on the smooth and rough plane surfaces. In addition, a considerable increase of the jet core length was indicated with increase of the jet Froude number. Results also showed a strong correlation between turbulence intensity coefficient and the jet core length.

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Main Subjects


  1. Fathi-Moghadam, M. A discussion on the model test report of the Dez dam low level outlets", Report No. P15466.00, produced by Acres International in association with Dezab Consulting Engineers submitted to the Khuzistan Water and Power Authority (KWPA), Ministry of Energy of Iran (2004). 2. Blair, H.K. and Rhone, T.J. Design of Small Dams, Chapter 10, Water Resources Technical Publication, U.S.B.R., Washington, USA (1977). 3. Kawakami, K. A study on the computation of horizontal distance of jet issued from ski-jump spillway", Proceedings of the Japan Society of Civil Engineers, 219, pp. 37-44 (1973). 4. Lencaster, A. Free overow spillway. Engineering and design principle", Report No. 174, National Lab for Civil Engineering, Portugal, Lisbon (1961). 5. Cola, R. Energy dissipation of a high-velocity vertical jet entering a basin", Proceedings of the 11th IAHR Congress, Leningrad, Russia (1965). 6. Beltaos, S. and Rajaratnam, N. Plane turbulent impinging jets", Journal of Hydraulic Research, 11(1), pp. 29-59 (1973). 7. Beltaos, S. and Rajaratnam, N. Impinging circular turbulent jets", Journal of Hydraulic Division (ASCE), 100, pp. 1313-1328 (1974). 8. Annandale, G.W., Scour Technology, Mechanism and Engineering Practice, McGraw-Hill, New York, USA (2006). 9. Castillo, L. Experimental and numerical methodology for the characterization of the pressures in the hydraulic energy dissipators" [Metodolog__a experimental y num_erica para la caracterizaci_on del campo de presiones en los disipadores de energ__a hidr_aulica], PhD Thesis, Polytechnic University of Catalonia, Spain, Hydraulics (1989). 10. Castillo, L.G. Pressures characterization of undeveloped and developed jets in shallow and deep pool", In Proceedings of the Congress-International Association for Hydraulic Research, 32(2), p. 645 (2007). 11. Manso, P.A., Bollaert, E.F.R., and Schleiss, A.J. Impact pressure of turbulent high-velocity jets plunging in pools with at bottom", Experiments in Fluids, 42(1), pp. 49-60 (2007). 12. Ervine, D.A. and Falvey, H.T. Behavior of turbulent jets in atmosphere and in Plunge Pools", In Proceedings of the Institution of the Civil Engineering, 83, pp. 295-314 (1987). 13. Ervine, D.A., Falvey, H.T., and Withers, W. Pressure uctuation on plunge pool oors", Journal of Hydraulic Research, 35(2), pp. 257-279 (1997). 14. Duarte, R., Schleiss, A.J., and Pinheiro, A. Inuence of jet aeration on pressures around a block embedded in a plunge pool bottom", Environmental Fluid Mechanics, 15(3), pp. 673-693 (2015). 15. Castillo, L.G. Parametrical analysis of the ultimate scour and mean dynamic pressures at plunge pools", International Workshop on Rock Scour Due to High Velocity Jets, EPFL, Swiss (2002). 16. Castillo, L.G. and Puertas, D.J. Discussion: Scour of rock due to the impact of plunging high velocity jets. Part I: A state-of-the art review (Bollaert, E. and Schleiss, A. 2003)", Journal of Hydraulic Research, 41(5), pp. 451-464 (2004). 17. Bollaert, E. and Schleiss, A. Physically based model for evaluation of rock scour due to high-velocity jet impact", Journal of Hydraulic Engineering, 131(3), pp. 153-165 (2005). 18. Bollaert, E. and Schleiss, A. Scour of rock due to the impact of plunging high velocity jets Part II: 698 M. Fathi-Moghadam et al./Scientia Iranica, Transactions A: Civil Engineering 26 (2019) 690{698 Experimental results of dynamic pressures at pool bottoms and in one-and two-dimensional closed end rock joints", Journal of Hydraulic Research, 41(5), pp. 465-480 (2003). 19. Ghaneeizad, S.M., Atkinson, J.F., and Bennett, S.J. E_ect of ow con_nement on the hydrodynamics of circular impinging jets: implications for erosion assessment", Journal of Environmental Fluid Mechanics, 15(1), pp. 1-25 (2015). 20. Kerman-Nejad, J., Fathi-Moghadam, M., Lashkarara, B., and Haghighipour, S. Dynamic pressure of _lip bucket jet", World Applied Sciences Journal, 12(8), pp. 1165-1171 (2011). 21. Puertas, J. Hydraulic design criteria of energy dissipation basins in arch dams" [Criterios hidr_aulicos para el dise~no de cuencos de disipaci_on de energ__a en presas b_oveda con vertido libre por coronaci_on], PhD Thesis, Polytechnic University of Catalonia, Spain (1994). 22. Castillo, L.G. Aerated jets and pressure uctuation in plunge pools", In Proceedings of the 7th International Conference on Hydroscience and Engineering (ICHE), Philadelphia, USA (2006). 23. Castillo, L.G., Carrillo, J.M., and Bl_azquez, A. Plunge pool dynamic pressures: a temporal analysis in the nappe ow case", Journal of Hydraulic Research, 53(1), pp. 101-118 (2014). 24. Castillo, L.G., Carrillo, J.M., and Bombardelli, F.A. Distribution of mean ow and turbulence statistics in plunge pools", Journal of Hydroinformatics, 19(2), pp. 173-190 (2017). 25. Castillo, L.G. and Carrillo, J.M. Comparison of methods to estimate the scour downstream of a ski jump", International Journal of Multiphase Flow, 92, pp. 171-180 (2017). 26. Castillo, L.G. and Carrillo, J.M. Scour, velocities and pressures evaluations produced by spillway and outlets of dam", Journal of Water, 8(3), p. 68 (2016). 27. Li, K.W., Pan, Y.W., and Liao, J.J. A comprehensive mechanics-based model to describe bedrock river erosion by plucking in a jointed rock mass", Environmental Earth Sciences, 75(6), pp. 1-17 (2016). 28. Davies, J.T., Turbulence Phenomena, Academic Press, New York (1972). 29. Arndt, R.E.A. and Ippen, A.T. Turbulence measurements in liquids using an improved total pressure probe", Journal of Hydraulic Research, 8(2), pp. 131- 157 (1970). 30. Salemnia, A. Dynamic pressure of vertical and circular free water jets on rough surfaces", M.Sc. Thesis, Shahid Chamran University, Ahvaz, Iran (2012).